There are many kinds of bad movies. Technically bad and lazily made movies, offensive movies, ludicrous movies (sometimes this isn't a problem), and deluded movies that try too hard. "Nativity 2" manages to be every single one of these, which is a shame, because it obviously means well.
NOTE: This film was made for Children in Need, and in good spirit. That doesn't make up for its quality, but at least gives it a sense of worth, since it was for charity. The kids at least seemed to have a good time.